Conventionally, spiral heat exchangers are manufactured by means of a winding operation. The two sheets are welded together at a respective end, wherein the welded joint will be comprised in a center portion of the sheets. The two sheets are winded around one another by use of a retractable mandrel or the like to form the spiral element of the sheets so as to delimit two separate passages or flow channels. Distance members, having a height corresponding to the width of the flow channels, are attached to the sheets.
After retraction of the mandrel, two inlet/outlet channels are formed in the center of the spiral element. The two channels are separated from each other by the center portion of the sheets. A shell welded onto the outer periphery of the spiral element. The side ends of the spiral element are processed, wherein the spiral flow channels may be laterally closed at the two side ends in various ways. Typically, a cover is attached to each of the ends. One of the covers may include two connection pipes extending into the center and communicating with a respective one of the two flow channels. At the radial outer ends of the spiral flow channels a respective header is welded to the shell or the spiral element form an outlet/inlet member to the respective flow channel. Alternatively, one single sheet is used for the manufacturing of the heat exchanger.
To enable the cleaning of the spiral heat exchanger different solutions has been used in the past. In GB-A-2 140 549 is disclosed a heat exchanger having a central passage body with a central spiral body. Cover plates are flanges onto the both sides of the central passage body. The flow channel of the spiral heat exchanger is thereby easy accessible for cleaning. In another document, U.S. Pat. No. 4,546,826, is disclosed a conventional spiral heat exchanger having a shell comprising three parts, a mid-section and two sections. Flanges of the end sections are attached to corresponding flanges of the mid-section.
In GB-A-1 260 327 is disclosed a heat exchanger having spiral tubular coil members housed in a shell. The shell has an upper section and a lower section, which are joined by flanges and bolts.
One problem with the conventional spiral heat exchangers are that they do not enable the replacing of the spiral body formed by the sheets if it is worn as the spiral body is welded to the cover or shell of the spiral heat exchanger.